This invention relates to position tracking systems, and, more particularly, to a system for detecting the angular position of a radiation source with respect to a radiation sensor.
It is known to sense a radiation source with a radiation sensor for measuring the relative position of the two. For example, U.S. Pat. No. 4,550,250 issued to Mueller, et al., discloses a system for detecting the position of a radiation source on a surface. This system employs a triangular-shaped detector fixedly positioned behind a slit aperture. Radiation from a radiation source passes through the slits and to the detector. As the radiation source moves in a plane (for example, along the surface of a table), the analog output signal from the triangular detector varies in proportion to the angle between the detector and the radiation source. The analog output from the detector is compared to a reference signal and digitized. The digital signals are then processed to determine the relative angle between the detector and the radiation source. The position of the radiation source in the plane is then calculated by triangulation.
Other known devices focus a point source of radiation onto an analog detector. The detector generates a pair of analog signals which are proportional to the angle of the detector with respect to the source in each of two orthogonal directions. Combinations of two or more of these analog detectors can be used to calculate the position and orientation of objects using triangulation algorithms.
In each case the analog output signal must be passed through an analog to digital converter and be subjected to significant additional processing. Each process step also limits the resolution Of the system, thus making fine measurements very difficult, if not impossible.